Circuit breaker



Feb. 5, 1935. J P E N 1,990,298

C IRCUIT BREAKER Filed June 13, 1929 2 Sheets-Sheet l Patented Feb. 5, 1935 UNITED STATES PATENT OFFICE Railway & Industrial Greensburg, Pm

Engineering Company,

a corporation of lfennayivania Application June 13, 1929, Serial No. 370,709

16Claima.

This invention relates to circuit breakers and more particularly to circuit breakers adapted for interrupting the flow of current on high tension lines.

The application is a continuation-in-part of my copending application Ser. No. 270,789, flied April 17, 1928.

An object of the invention is to provide a circuit breaker of such construction and such high speed of operation that the interruption of current flow is characterized by the substantial absence of arcing between the separating or separated contact members. An objectis to provide a circuit breaker in which the breaker terminals are separated at such high speed that the gap established during one-half cycle exceeds the distance over which the increasing voltage of the next voltage wave can establish arcing conductivity. A further object is to provide a mechanically actuated circuit breaker in which the actual break between the contact terminals is confined within an insulating tube of small bore, whereby the amount of ionization that can take place is reduced to a minimum. More particularly, an object of the invention is to provide a circuit breaker including a movable contact element which extends into and has an end yieldingly secured within an insulating tube of small bore, and operating mechanism for mechanically withdrawing the contact element from the tube at a high velocity, which operating mechanism may take the form of an explosive device or projectile. Further objects are to provide thermostatically controlled operating devices having predetermined time-response characteristics, and distribution systems in vwhich the several portions of the line may be protected by circuit breakers operable at the same predetermined overload conditions but calibrated for operation at different time interva I These and other objects of the invention will be apparent from the following description when taken with the accompanying drawings in which:

Fig. 1 is a side view in elevation of a circuit breaker constructed according to the principles of my invention; a

Fig. 2 is a fragmentary vertical longitudinal section through the circuit breaker;

Fig. 3 is a central longitudinal section through the thermostatic actuating device;

Fig. 4 is a transverse section on line 4-4 of Fig. 3; i

Fig. 5 is a transverse horizontal section taken along the line 5-5 of Fig. 2.

Fig. 6 is a circuit diagram of a distribution system equipped with circuit breakers embodying the invention.

Referring more particularly to the drawings, 10' designates a suitable support carrying the 5 usual insulating brackets 11 and 12. To the lower a bracket is secured a conducting member 13 which extends downwardly from the outer end of the bracket, and then upwardly at 14 where it is secured to a metal cap 15. A bracket 18 is also secured to the outer end of the member 12 and extends downwardly where it supports a bag or container 17 which is adapted to receive the movable contact element 18 when the circuit has been broken, as will be presently explained.

The insulating bracket 11 carries a metallic fixture 20 of appropriate form for the reception of a line terminal 21 and for supporting a metal cap 22, the terminal and cap being connected by the usual shunt 23.

Referring more particularly to Fig. 2, it will be seen that the cap 22 has a socket for receiving the threaded end of a brass ferrule 24 which is fixed to one end of an insulating tube 25, for example, by means-of screws 26. The tube may be formed of cloth or paper impregnated with a phenolic resin or other material having nonwarping, high insulating qualities. The tube has a small inside diameter and the walls are of sufflcient thickness to provide the mechanical strength required to withstand the high pressures which may be generated when a heavy current flow is broken.

One end of the contact element or strip 18 is impositively secured to the upper end of the fer- 35 rule 24, for example, by a pair of clamping elements 2'! which are brought together by means of a bolt 28. The contact element may take the form of a heavy wire, a metal strip or the like, but preferably, it comprises a flexible copper wire such as the ordinary seven strand bare copper antenna wire. A stop wire 29 is passed through the element 18 to leave a predetermined length thereof outside of tube 25, and the lower end of the element carries an eyelet 30'for effecting connection with the actuating mechanism of the circuit breaker. The length of the tube 25 and contact element 18, depends, of course, upon the voltage employed in the circuit.

The actuating mechanism comprises a temperature-controlled explosive cartridge which 'may conveniently take the general form of a shotgun shell. As shown in Fig. 3, the shotgun shell, having a flanged metal base 31 and shell 32,

Q soldered or sweated to the base 31 and to a rod or heavy wire 34', the rod projecting beyond the outer end of shell 32 and terminating in a thread ed lug 35, which, with wingnut 36, provides means for securing the eyelet 30 of contact strips 18 to the cartridge.

To permit accurate calibration of the ignition wire 33, the inner end of rod 34' carries a bridge strip 37 which rests upon a ring 38 to determine the length of the ignition wire. The usual wadding 39 is employed and a sealing compound 40, of viscous material of low melting point, fills the major portion of the space above the wadding. The end of the shell is closed by a fiber washer 41, a metal washer 42 which may be soldered or otherwise fixed to rod 34', and a layer 43 of a hard sealing compound.

As shown in Fig. 2, the metal cap 15 of the lower insulating support is provided with a socket for receiving the explosive cartridge which is secured in place by the sleeve or barrel 44, the outer end of the barrel being provided with ribs 45 or other appropriate tool engaging means.

The actuation of the circuit breaker is initiated by the heating of the ignition wire 33 when the current fiow rises to a dangerous or otherwise undesirable magnitude. When this occurs, the explosive is ignited, and the packing and rod 34' are violently expelled from the shell.

Although the barrel is quite short, the high explosion pressure will impart a high acceleration to the moving system after breaking the imiligsitive connection at the upper end of element The rapid acceleration of the contact element 18 is an important feature of the invention, and for any given installation, the quantity of explosive employed is regulated to effect separation of the breaker contacts at such high velocity that the gap established in one-half cycle is greater than the distance across which the voltage can establish arcing conductivity.

, Although the circuit breaker interrupts the line at two points, I'believe that the real break occurs between the contact element 18 and the clamp member 27 since the high temperature established by the explosive charge may be suflicient to afford a conductive path between the rod 34' and .the adjacent portions of the cartridge support.

After actuation of the circuit breaker, it may be ,restored to operating condition by replacing a new cartridgefin the socket of cap 15 and by removing the insulating tube and connecting the end of another contact element 18 in the clamp member 27. The tube is then replaced in the cap 22 and the eyelet of the contact element is fixed to the post of rod 34 by means of th wingnut 36. I

The employment of the insulating tube 25 for controlling the conditions under which the break occurs is an important feature of the present invention. The final break of an alternating current, when two contacts are separated, will of course occur at or near ero voltage. To prevent the increasing voltage 0 the. next half wave from re-establishing the current flow, theconductivity across .the gap must be reduced by increasing the separation of the contacts and/or by reducing the conditions tending to effect ionization.

Since the contact element 18 is mechanically withdrawn from the clamp, the initial separation is not preceded by the fusing or volatilization of any metal. If the initial separation is accompanied by any arcing, the high pressure due to heating of the air within the tube and possibly to some metal vapor, tends to prevent the formation of an ionized path and also assists in the rapid expulsion of the contact element from the insulating tube.

When employed on direct current lines, the breaker contacts should be separated at approxi-' mately the same high velocities as would be set by the half-cycle standard on alternating current lines. I am not now able to specify a definite rule for determining the velocity at which direct current contacts should be separated, but by analogy to the conditions observed on alternating current lines, I believe that the time interval for effecting withdrawal of contact element 18 from the expulsion tube 25 should be of the order of not less than one one-hundredth of a second.

The composition, length and diameter of the ignition wire 33 are so related that the wire will be raised to a red heat or ignition temperature by the passage of a current which exceeds the rated current-carrying capacity of the cartridge by a predetermined amount, for example, fifty percent. Materials which I have found suitable are copper, German silver and nickel, all ofwhich have melting points well above the ignition temperature of the black or smokeless powder which I employ in the explosive shells. Particular attention is directed to the fact that the ignition wire is not a fuse since the actuation of the circuit breaker is not determined by the fusing or volatilization of the wire. The usual low temperature fuse wires cannot be closely calibrated since oxidation will change the effective crosssection if the fuse is operated for extended periods at temperatures close to the fusion point of the soft alloy. The present ignition wire is designed for operation at a relatively low temperature and therefore the cross-section of the. wire is not materially affected by oxidation even though the current flow is such that the wire is held for long periods at a temperature close to its operating point.

Attention is also directed to the fact that the explosion of the charge is not the immediate result of the flow of an abnormally large current, since the thermostatic control wire 33 must be raised to the ignition temperature of the powder to initiate the action. For a given increase in current flow, the rate at which the temperature of the wire increases is a function of the mass of the wire, and it is therefore possible to deter-; mine the time response characteristic of a single circuit breaker, or the relative time response characteristics of a plurality of circuit breakers, by an appropriate choice of the material constituting the ignition wire.

For a given current, the relative masses' of ignition wires of different compositions will vary inversely as their relative conductivities. For example, a copper wire will be of smaller sizeand mass than a German silver wire, and a German silver wire will be of smaller size and massthan a nickel wire.

This variation in the time response characteristics of different metals may be employed to- 1,sso,aos

of branch lines E, and which are separated from each other by circuit breakers of the type herein described.

In the diagram, noattempt has been made to illustrate the mechanical construction of the circult breakers, and the relative masses of the several ignition wires are graphically indicated by the relative widths of the lines. The ignition wires T of the circuit breakers protecting the several branches E and the terminal section D are of relativelyflne wire of high conductivity, for example, copper; the ignition wires '1" which form parts of the circuit breakers between sections B and C are formed of wire of somewhat lower conductivity, for example, German silver; and the wires '1 are of still lower conductivity, for example, nickel. Although all of the ignition wires are calibrated for the some normal current flow, and are intended to elect actuation of the respective circuit breakers when the current increases to approximately fifty per cent above their rated capacity, the presence of an overload or short circuit on one part of the system will not effect actuation of all of the circuit breakers.

Assuming that one of the branch lines E or terminal section D is overloaded, the abnormal flow of current will raise the temperature of the particular ignition wires T at a more rapid rate than thetemperatures of the heavier wires '1" and T". The branch and/or terminal circuit breakers will therefore be actuated to isolate the overloaded circuit before the circuit breakers which protect sections B and C are actuated.

While I have described the invention as embodied in an overload circuit breaker, it will be apparent that the invention mayebe employed for the interruption of current flow in high tension lines by d the actuating device for manual operation.

It will be apparent that various changes may be made in the various parts, their relative size, shape 'and relationship without departure from the spirit of my invention as set forth in the following claims.

I claim:

1. In a high tension circuit breaker, the combination with an elongated expulsion tube of insulating material, a metallic contact closing one end of said tube, and a contact element extending through said tube and yieldingly engaging said metallic contact, of thermostatically controlled means for mechanically withdrawing said element from said tube at high velocity.

2. In a high tension switch, the combination with an elongated expulsion tube of insulating material, and circuit elements forming a conductive metallic path through said tube, of mechanical means for withdrawing one of said elements from said tube to effect a break in said conductive path, said mechanical means constituting the sole means for withdrawing said element and including traction means whose rate of movement is independent of the magnitude of the current flowing through said conductive path, and means forinitiating the movement of said tractive means.

3. In a high tension switch, the combination with an elongated expulsion tube of insulating material, and circuit elements forming a conductive metallic path through said tube, of mechanical means'for withdrawing one of said elements from said-tube to effect a break in said conductive path, said mechanical means including traction means whose rate of movement isindependent of the magnitude of the current flowing through said conductive path, and means operable upon predetermined current flow conditions to initiate the movement of said tractive means.

4. In a high tension circuit breaker, the combination with solid contacts positioned within and engaging each other adjacent the end of an expulsion tube, of mechanical means connected with one of said contacts and capable ofapplying thereto a force eflective to withdraw the said connected contact from said tube at such high velocity that current flow will be interrupted in substantially one half-cycle, and means actuated by predetermined conditions of current flow for initiating the movement of said mechanical means to cause the application of such force to said connected contact.

5. A circuit breaker comprising a contact element, a tube formed of insulating material for housing a portion of the contact element, means at the inner end of the. tube for attaching one end of the contact element to a fixed contact, a cartridge having explosive materials spaced from the free end of the tube, a projectile carried by the cartridge and connected with the projecting end of the contact element, and an ignition element embedded in explosive material and connected to the projectile.

6. A circuit breaker comprising a contact element, a tube formed of insulating material for housing a portion of the contact element, a fixed contact at the inner end of the tube, means for attaching said contact element to said contact, a cartridge having explosive materials spaced from the free end of the tube, a projectile carried by the cartridge and connected with the projecting end of the contact element, an ignition element embedded'in explosive material and connected to the projectile, a receptacle located adjacent the cartridge adapted to receive the contact element and projectile when the latter are forced from their normal positions upon ignition of the explosive material.

'I. A circuit breaker comprising a contact element, a tube formed of insulating material for housing a portion of the contact element, a metal ferrule secured to one end of the tube, means for clamping an end of the contact element in the metal ferrule, a cartridge having explosive materials spaced from the other end of the tube, a projectile carried by the cartridge and connected with the projecting end of the contact element, an ignition element embedded in explosive material, and circuit elements connecting said contact element and said ignition element in the path of current flow.

8. A circuit breaker comprising a contact element, a tube formed of insulating material, a contact at one end of said tube, a portion of said contact element extending into said tube, means for clamping one end of the contact element to said contact, a cartridge having explosive materials spaced from the free end of the tube, a projectile carried by the cartridge and connected with the projecting end of the contact element, an ignition element embedded in explosive material and connected to the projectile, and means on said contact element for limiting the inward movement thereof into the tube.

9. In a circuit breaker, a contact element connected between two ilxed contacts, means for removing said element from engagement with said contacts, said means comprising a cap, a barrel screwed into the cap, a cartridge mounted in the barrel and having a chamber provided with explosive material, an ignition element havof the contact element to the free end of the projectile.

10. An electrical circuit breaker of the type including a pair of terminals, an elongated expulsion tube carried by one terminal and having one open end, and a circuit between said terminals including a conducting wire extending into said tube, characterized by the provision of explosive means for forcibly breaking said circuit at a point remote from the open end of said tube and for forcibly removing said condue ting wire from said tube, said explosive means comprising a case housing an explosive charge, and an ignition wire in said case and forming part of said circuit.

11. An explosive circuit breaker comprising the combination with two line terminals, an elongated expulsion tube of insulating material, and a conductor extending into said tube, of an ex-- plosive cartridge for removing said conductor from said tube, said cartridge including a shell containing an explosive, and an ignition wire in said shelland forming a part of an electrical- 12. In a circuit'breakena pair of gap-spaced terminals, an expulsion tube substantially spanning the gap between said terminals, a circuit including a flexible conductor within saidtube, and means operative upon an overload for mechanically breaking theicircuit within said tube and for removing said flexible conductor therefrom.

13. In a circuit breaker, a continuous unbro-' stantially bridging the gap between said terto' initiate the operation of said mechanicalv means.

15. A circuit breaker as claimed in claim 14, wherein said mechanical means comprises a source of potential energy positioned outside of said tube. I

16. A circuit breaker as claimed in claim 1 wherein said mechanical means comprises an explosive charge and a projectile positioned outside of said tube.

, JOHN P. MEDLIN. 

